An undesirable phenomenon known as "white smoke" is a frequent side effect of no load or light load diesel engine operation at low temperatures. This phenomenon is essentially the result of unburned hydrocarbons in the engine exhaust and is attributable to misfiring or incomplete combustion in some or all cylinders. White smoke is both a respiratory and optical irritant as well as adversely affecting visibility. While white smoke is not a regulated exhaust emission, sociability of the engine or vehicle suffers as a result of the production of white smoke.
Various prior art devices have been employed to effectuate the transfer of heat to the intake air of a diesel engine. One such electrical heating system is disclosed in U.S. Pat. No. 5,094,198 to Trotta et al., assigned to Cummins Electronics, Inc. Trotta et al. discloses a method and apparatus for preheating intake manifold air prior to starting the engine, and for postheating the intake air while the engine is running. In so doing, a pair of intake manifold air heaters are each activated for predetermined durations, and at predetermined duty cycles, according to specific ranges of intake air temperature.
The ability to monitor such intake air heating systems has been mandated by the California Air Resources Board (CARB) as part of the On Board Diagnostics (OBD) II program targeted for vehicles having internal combustion diesel engines. Since the failure of an intake air heating system may increase emissions during cold starts, CARB has taken the position that, for sociability reasons, such a system must be monitored for certain faults and failures. Under OBD II, the integrity of intake air heating system components must be continuously monitored, and the driver made aware of faults and failures which require service. It is thought that by immediately warning the driver of a fault or failure within the intake air heating system, such a condition is likely to be timely serviced. Beginning with the 1996 model year, manufacturers of vehicles having diesel engines that fail to comply with OBD II will be forbidden from selling such products in the California market. It is possible, however, for such manufacturers to obtain a one year extension from CARB in order to meet the ORD II requirements.
In order to address these and other concerns, as well as shortcomings of the prior art, the present invention provides a system and method for heating intake manifold air to reduce white smoke while providing continuous diagnostic testing of the various system componentry. Such a system complies with OBD II by continuously warning a driver, under certain conditions more fully described hereinafter, of an existing fault or failure condition within the intake manifold air heating system.